Workpiece holder



Aug. 26, 1969 J. RECH 3,463,477

WORKPIECE HOLDER Filed April 11, 1956 INVENTOR.

JAKOB RECH iZQ/M ATTORNEY United States Patent 3,463,477 WORKPIECE HOLDER Jakob Rech, Detroit, Mich., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed Apr. 11, 1966, Ser. No. 541,782 Int. Cl. B25b 1/24, /16; B21d 37/14 US. Cl. 269-265 3 Claims ABSTRACT OF THE DISCLOSURE In a pressure-kneading operation, such as the formation of accurately dimensioned steel type on the periphery of a steel wheel, the pressures required to form the type character and to cause the steel to become plastic enough to flow into the matrix being used are so great that the blank will be distorted by the metal working operation.

This invention has as an object a clamping mechanism for a metal blank, such as a steel blank, which maintains the body of the blank in undistorted condition even during extensive pressure working of the surface.

When a number of different characters are generated around the periphery of a metal blank, for example, a steel wheel, in one process the characters are generated individually. A matrix which is caused to have an oscillatory motion with respect to the blank contacts the blank under extremely high pressure and performs a kneading action. The local pressures in the metal exceed the elastic limit of the material and cause the metal to become plastic and therefore to flow into the recesses of the matrix to form the character on the edge of the blank.

To position each individual character with respect to the other characters on the periphery of such a metal type wheel with high precision, has previously posed considerable problems in character location. Often such characters must be positioned within 0.0005" to 0.001". It has been known to locate a character on a workpiece being manufactured by a mechanical indexing locator which operates in conjunction with the previously formed character. If the portion of the previously formed character has been perfectly fabricated and offers a sharp, reliable portion, it is possible to stay Within the narrow tolerances required by todays printed materials. Even so, the skill required of the machine operator to achieve accuracy in the location of a previously formed character is very high, and the performance of the locating operation is very time consuming.

It is another object of this invention to enable a character to be exceedingly accurately located on the periphery of a workpiece without the intervention of separate locators, and without depending upon the skill of the operator for character location.

It is also an object of the invention to provide a reference point for characters on a workpiece as an incident to the manufacturing operation, which reference point may be used in subsequent machine operations.

Briefly, in accordance with this invention, a workpiece holder is employed to clamp a workpiece being operated upon by pressure metal forming which utilizes strain relieving members which indent the workpiece to transfer the pressure from the workpiece to the holder. The workpiece clamp contains as an integral component of one of c we the clamping jaws some raised portions which indent the workpiece with grooves transverse to the direction of the stress. The other jaw of the clamping device has a number of points extending from the clamp equally spaced around a circular blank. The number of reference points used is equal to the number of individual forming operations to be carried on around the blank. For example, if there are seventeen characters to be formed around the periphery of the workpiece, one jaw of the clamp will contain seventeen equally spaced points which indent the blank the first time that the workpiece is locked up in the clamping operation, and which serve as locating indentations for subsequent operations.

The blank being worked upon then has a number of locating indentations precisely positioned with respect to the characters generated on the periphery of the workpiece. Subsequent machining operations can then be performed using the indentations referred to as locating marks for such operations without any error of registration.

Further, the act of forming all of the indentations by the first clamping action of the workpiece holder eliminates the subsequent dependence upon operator skill to locate the blank with respect to the remaining operations.

A more detailed description follows in conjunction with the accompanying drawing, wherein:

FIG. 1 illustrates diagrammatically a workpiece holder in accordance with the invention for use with a pressurekneading system;

FIG. 2 shows a blank utilized in a type wheel making operation;

FIG. 3 is a perspective view of one of the clamping members;

FIG. 4 is a perspective view of the other of the clamping members showing the locating indentation points; and

FIG. 5 is a perspective view of the reverse side of the blank shown in FIG. 2.

Referring now to FIG. 1, a metal working matrix 11 is caused to oscillate back and forth to perform a knead ing action, such as, for example, by means of an eccentric drive shaft 13. The drive shaft 13 oscillates the matrix 11 from side to side, but due to the slot in which the drive shaft 13 operates does not cause any up and down component to be transferred to the matrix 11. Although simplified in the diagrammatic view of FIG. 1, the motion of the kneading head 11 actually pivots about the surface at the bottom of the engraved matrix which forms the top of the type character. The downward motion of the matrix 11 is caused by the travel of a lever 15. The lever 15 is pivoted about a shaft 17, and is driven, for example, by a rotary cam 19 by an appropriate prime mover.

A metal blank 21 upon which indicia are to be formed under the kneading operation of the matrix 11 is inserted between the two jaws 23, 25 of the workpiece holder. The jaw 23 is caused to clamp the workpiece 21 in combination with the jaw 25, for example, by means of a hydraulic cylinder 27 connected to a pivoted lever 29 acting directly upon a shaft 31 which carries the jaw 23. It will be understood that all of the various parts referred to, including the levers 15 and 29, the hydraulic cylinder 27, the jaw 25, the prime mover for cam 19 and the means to oscillate the shaft 13 are all secured to the frame of the machine, which is not shown for the sake of simplicity.

The jaw 23 which is also shown in FIG. 3, has one or more ridges 33 which may be triangular in form to better grip the metal blank 21. The ridges 33 may, of course, have any other convenient cross-sectional configuration, such as rectangular or semi-circular.

The jaw 25, which is also shown in perspective in FIG. 4 as well as in cross-section in FIG. 1, has a plurality of short circular bar-like protrusions 35. These protrusions 35 are equal in number to the number of individual characters to be worked into the periphery of the workpiece 21. These protrusions or points 35 are equally spaced around the center of the jaw on a circle near that radius on the blank which is contacted by the ridges 33 carried on the other jaw 23. Ideally, if two circular ridges are contained on the jaw 23, the protrusions 35 carried by the jaw 25 can be made to fall between the two circles 33. When placed in this manner the raised protrusions'on the jaw 25 are radially displaced from the raised protrusions of the jaw 23 during engagement of the workpiece 21.

When kneading pressure is applied, and the matrix 11 comes into contact with the blank 21, the compression between the matrix and the center of the metal blank has to be great enough to cause the steel to become plastic and flow into the matrix. This pressure is also great enough to cause the blank to be distorted because of compressive forces beyond the elastic limit of the metal between the matrix 11 and the center shaft 37. The ridges 33 and the protrusions 35 extending into the blank 21 between the point where the periphery of the wheel is being kneaded and the center shaft 37 act to transfer the stress from the workpiece 21 to the jaws 23, 25 of the workpiece holder.

Two releasing pins 38 are operated by mechanical means such as hydraulic cylinders 40 to push the workpiece blank 21 off of the center shaft 37 and to free the blank 21 from the protrusions 35.

FIG. 2 is a perspective view of one side of a workpiece which shows the indentations 39 which are made during the clamping action by the protrusions 35. Additionally, some teeth 41 are shown in FIG. 2 which are adapted to be engaged by the matrix 11 and kneaded to form the characters shown at 43 of this figure.

FIG. 5 shows a perspective of the other side of a workpiece 21 which illustrates grooves 45 made in the workpiece by the ridges 33 on the face of the jaw 23. Blank teeth 41 like those of FIG. 2 are shown in this figure as well, and the sensed characters are illustrated at 43.

FIGS. 2 and 5 illustrate a composite of several sequential operations. It is found advisable in the actual manufacturing process to first clamp a perfectly circular blank 21 to put the indentations 39 and the grooves 45 in the blank. In a subsequent machining operation, the teeth 41 can be formed to provide a blank which is most receptive to the kneading process. In this blanking operation in which the teeth are formed, the indentations 39 are used as locators. The blank 21 is then clamped between the jaws 23 and 25 with a chosen tooth 41 precisely positioned by means of the indentations 39 engaging the protrusions 35. The matrix 11 is brought into contact with the tooth 41 while it is being oscillated back and forth (side to side as shown in FIG. 1).

Different matrices may then be used sequentially to form different characters at all of the character positions around the periphery of the wheel. For each of these operations, the indentations 39 precisely position the workpiece 21 for the kneading operation. After all of the characters 43 are generated around the entire circumference of the wheel as desired, the flared metal is trimmed otf in a machining operation, and the type wheel may be hobbed in between the characters to allow it to be driven by a rack or a mating pinion as desired.

FIGS. 3 and 4 show the two jaws of the workpiece holder which is used to clamp the blank 21 of FIG. 2 or FIG. 5 during the kneading operation described above in conjunction with FIG. 1. The individual type characters 43 are formed at each tooth location 41 by a separate kneading operation. During each kneading operation, the pressures generated by the matrix 11 on the workpiece 21 are so great that without the support of a workpiece holder in accordance with this invention to transfer the stress, the workpiece 21 will fail in shear or compression. Furthermore, without such holder, as each individual character 43 is kneaded, the blank 21 is made out of round because of the creep of the metal with the latest kneading operation.

The raised portions 33 on the face of the jaw 23 shown in FIG. 3 indent the workpiece with grooves transverse to the direction of stress. These grooves in the workpiece 21 cause the stress induced by the kneading operation to be transferred from the workpiece into the jaws of the holder.

Likewise, in the other jaw shown in FIG. 4, the pins 35 extend directly into the body of the workpiece a sufiicient amount to absorb the stress and prevent the creep or collapse of the workpiece 21. The jaws 23, 25 have greater strength than the blank 21 and can withstand the stress of the operation without deformation.

Regardless of how tightly the workpiece is held in compression between two perfectly smooth jaws, it was found that the hole in the center of the blank tended to collapse on the center shaft 37 so that the blank 21 could not be removed. Jaws having the protrusions 35 and the raised portions 33 to actually indent the workpiece 21 yialded a perfectly round finished workpiece, and prevented the axial collapse or failure in compression or shear.

I claim:

1. A workpiece holder for use in conjunction with a circular workpiece which is to be operated upon by pressure metal forming techniques around the circumference of and directed substantially radially toward the workpiece comprising a pair of clamping jaws, both of said jaws having as an integral component of the face thereof raised portions which during engagement of the workpiece indent and extend into the workpiece and leave permanent indentations, the raised portions of one of said jaws being a number of protrusions from the face of said jaw arranged on a circle of a first given diameter, the raised portions on the other of said jaws being arranged on a circle of a second given diameter different from said first diameter, whereby said raised portions on said one jaw are radially displaced from said raised portions of said other jaw during engagement of a workpiece by said aws.

2. The combination as defined in claim 1 wherein the raised portions on said second jaw comprises a protruding ring adapted to indent the workpiece with a groove transverse to the direction of stress induced during a pressure forming operation.

3. The combination as defined in claim 1 wherein the raised portions on said second jaw comprise a pair of protruding rings, one of said protruding rings having a diameter larger than the diameter of the circle on which the protrusions on said first jaw are located, the other of said rings having a diameter smaller than said circle on said first jaw.

References Cited UNITED STATES PATENTS 4/ 1876 Wilcox 72474 7/1932 Merrill 72412 X US. or. X.R. 72 474 

